I wrote this post a while back. The content can still be relevant but the information I've linked to may not be available.
I have been geotagging a pub guide website using the geo microformat. Each of the pubs has an Ordnance Survey map reference and it’s quite easy to wrap this with an
<abbr> tag and its attributes like this:
<abbr class="geo" title="latitude;longitude">OS Map Ref</abbr>
This type of microformat information adds more meaning/data to your website and potentially opens up the website for use by other web applications. In my opinion, geotagging and the use of location-based information will become more important in future.